1. Technical Field
The present invention relates generally to pushbutton switches and particularly to a dome contact used in pushbutton switches and method for fabrication the dome contact.
2. Description of the Related Art
Keypads are widely used for inputting data in the user interfaces of portable electronic devices such as mobile phones, personal digital assistants (PDAs), etc. As shown in FIGS. 7 and 8, a pushbutton switch 100 of a keypad typically includes a button 12, a dome contact 13, and a fixed contact 15. The button 12 is mounted to a housing 10, and has an outer surface exposed from the housing 10 to be pressed by a user. The button 12 includes a bump 125 projecting from a central portion of an inner surface thereof. The dome contact 13 includes a diaphragm 130 and a contact sheet 132. The diaphragm 130 is made from an electrically insulative elastic material. The diaphragm 130 can be actuated from a first dished configuration to a second, opposite dished configuration by external force and, then rebound to the first dished configuration after the external force is released. A central portion of a convex surface of the diaphragm 130 faces the bump 125 of the button 12. The contact sheet 132 is made of electrically conductive material, and is adhered to a central portion of a concave surface of the diaphragm 130. The fixed contact 15 is mounted to a circuit board 17, and faces the contact sheet 132. When the button 12 is pressed, the bump 125 of the button 12 presses against the dome contact 13. The dome contact 13 is elastically deformed, and the contact sheet 132 contacts the fixed contact 15 thereby generating an input signal.
However, when making and assembling the pushbutton switch 10, the bump 125 of the button 12 may be disposed unaligned with the center of the dome contact 13. In this condition, pressing the button 12 requires additional force, and the pushbutton switch 10 cannot provide a desirable tactile feedback characteristic. In addition, since the dome contact 13 is likely to be pressed from its center, the reliability of the contact between the contact sheet 132 and the fixed contact 15 is affected.
Therefore, there is a need to provide an improved dome contact and a method for making the dome contact to overcome the above-described problem.